Recombinant human insulin-like growth factor-I (rhIGF-I) was iodinated using a lactoperoxidase-catalyzed labeling method. The labeled products were separated into more than five fractions by ion-paired reverse-phase high performance liquid chromatography (HPLC). A fraction (peak 1), which showed the highest yield and radiactivity, was found to be biologically active in the BALB/c 3Ts cell proliferating system. The site of the iodination was investigated by S-pyridylethylation followed by trypsinization and separation with HPLC using reverse phase columns. From the amino acid analysis of the peaks which were radioactive, the iodination site of peak 1 was revealed to be Try-24 and Try-60. This is the first report of the biological activity of radioactive peptide hormone with a defined laveled site.
Kohama, Y., Okabe, M., Tsujikawa, K., Oka, H., Teramoto, T., Kayamori, Y., Itoh, M., & Mimura, T. (1992). Preparation of Biologically Active and Site Specifically Radioiodinated Recombinant Human Insulin-like Growth Factor-I. Chemical and Pharmaceutical Bulletin, 40(3), 808-810. https://doi.org/10.1248/cpb.40.808